The Frailty Of Genius
by Emeraldbuttercup
Summary: When a case begins to unravel Sherlock's secrets...
1. Chapter 1

**Rated T for the same language and gore found in the Sherlock series.**

* * *

John swore under his breath, pressing his body against the worn brick wall. With a flick he turned off his torch, and darkness consumed him. His breathing was slightly elevated, though not from physical exertion. Once again he cursed venomously, his firm grip on his torch tightening.

Sherlock was in danger. Damn that pompous detective, always rushing headlong into trouble. Hadn't bothered to wait up for John, hadn't bothered to call for backup. His massive intellect coupled by his fever for constant stimulation was constantly getting him caught in dodgy situations like these.

John, out of a habit he had adopted in Afghanistan, tapped his side where his handgun was concealed. His soldier's mind analyzed his surroundings as his eyes adjusted to the dark.

In the gloom, John could just make out a concrete statue of a coiled serpent. Its wide, unseeing eyes seem to penetrate him coldly, calculatingly. A few meters away was a small building, large glass windows dimly illuminated with green light.

The Snake House.

John slowly detached himself from his comfortable hiding place, slinking in the shadows towards the building. His mind narrowed onto his mission, his eyes darting around to recognize any possible threats. He appeared to be alone, but he did not let his eyes deceive him. Sherlock had come here for a reason. It was all connected to the case.

A gunshot pierced the cold night, ringing out from within the snake house. For a flicker of a moment, John could have sworn his heart stopped.

Sherlock was in there.

He was unarmed.

John, abandoning stealth all together broke into a run, throwing the torch onto the ground and reaching into his jacket. Terror seeped throughout his body, raw, undiluted fear that he had not experienced since his drug-induced paranoia at Baskerville. His brain went into over-drive, adrenaline roaring through his veins. John took his handgun out of its holster in his jacket and clenched it in his right hand. Not bothering to look down at what he was doing, John flicked the safety on the gun off with a practiced move. He barged towards the snake house, ignoring his instincts that were screaming that he was running into a trap. His heart was lodged in his throat as he imagined Sherlock, bleeding on the unforgiving floor- with a strangled yell, John threw himself at the snake house.

His bad shoulder screamed in protest as his entire side exploded in pain, but John couldn't care less. He rammed himself into the door repeatedly, his jaw clenching with determination. He would _not_ let Sherlock get hurt, he could not. Pain and fear and rage all seeped together to form a lethal concoction. With an inhuman yell, the deadbolt broke and the door finally swung open. He rushed into the darkness, his gun held steadily in his hands. John looked around cautiously, his eyes trying to pick up on the slightest movement. All around him the glass exhibits shown with unearthly low green light. Reptiles slithered and crawled, their many-lidded eyes watching the army doctor with dumb curiosity. John walked farther into the room, his footfalls slow and cautious. The hairs on the back of his neck stood up, and perspiration dotted his brow.

John felt the air stir and knew what was happening an instant before it happened. He whirled around as the broken door slammed shut. John held his handgun out, the barrel aimed in the direction of the door.

"The police are here," John said calmly, praying that whoever was in this foul place would believe the lie.

"Surrender when you still can." There was a silence that followed John's forceful words. Something wasn't right…

Suddenly there was light, bright and blazing light. John stumbled back, blinded.

A scream punctured the air.

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_Four Days Ago:_

It was at an ungodly hour early Tuesday morning when a disgustingly energetic Sherlock had rushed a very indignant John out of bed. The younger man had practically dragged the army doctor down the stairs from their flat. Once on the street Sherlock proceeded without further adieu to manhandled John into the waiting cab, after which he fairly flew to the other side of the cab and climbed inside in a tangle of uncoordinated long limbs. The gleam in Sherlock's eyes shone bright with maniac glee, causing John's stomach to sink unpleasantly into the floor of the cab. He knew that look. It was the gleam that was usually followed by Sherlock doing something dangerous or idiotic or both. That look- the slight self-satisfied curve at the ends of his mouth, the smugness of the arched eyebrows- meant trouble. Sherlock raised his coat collar up, turning to face the still half-asleep John. The light in the cab cast shadows from the consulting detective's cheekbones, which sent a thrill of irritation through John's bleary mind.

Bloody cheekbones.

Sherlock being Sherlock gave absolutely no useful information to John during the car ride to the crime scene as to the details of the case. But one didn't have to be the world's only consulting detective to deduce the bare essentials. John could tell by Sherlock's tight smile and fingers tapping impatiently on his lap that the case must be ranked at least an eight, if not a nine, on Sherlock's imaginary scale of importance. John figured it had to be nothing short of a double homicide to get Sherlock moving about so quickly. Sherlock was normally disinclined to obey someone else's orders quickly, the stubborn arse. John peered out the window, noticing that the sun hadn't even risen above London skyline. God, it had to be at triple homicide then.

Imagine John's surprise then, when the cab stopped in front of the London Zoo. John had unabashedly let his jaw drop at the sight of the sickly pink cotton candy machines and bunches of cartoon animal balloons. There was no blood pooling on the cement or a grisly signs of a knife fight. There even weren't any ambulances or fire trucks, for Christ's sake. Only a handle full of police cars and a caution tape barricade near the zoo's entrance. Lestrade was pacing in the front of the main gate, his cell phone pressed against his ear. Judging by his violent hand gestures, he was greatly agitated. Sherlock scrambled out of the cab without a second's hesitation, his dark curls flying about in the wind. He ran across the street, his coat billowing around him impressively. John sighed in resignation as he fished out his wallet to handle the tab for the bewildered cabbie.

By the time John managed to catch up with him, Sherlock was already quickly wearing on Lestrade's patience with his rapid-fire assault of questions.

"Time?"

"My team guesses it was less than three, maybe four hours ago."

"The area has been searched?"

"'Course it has! All clear."

"You're quite sure? Your team has proven incompetent before, and I would hate for the entire case to be blown because Anderson had his attention compromised by Donovan's close proximity."

"Bloody hell, Sherlock-!"

"Greg," John said, interrupting the Detective Inspector. Lestrade's reddened face calmed a bit in John's presence, though he still shot Sherlock a dirty look. John shook Lestrade's hand solidly before standing at attention, always the soldier. "Could you explain the situation to me? Sherlock couldn't be bothered." Sherlock gave John a hurtful frown.

"You could just have asked."

"I did, Sherlock. Seven times to be exact, on the way over."

"I was in my mind palace. You know better than to interrupt me when I'm thinking." John rolled his eyes.

"If you listened only when you weren't thinking Sherlock, you'd be deaf."

"Was that a compliment?" Sherlock asked cheekily, smirking at the light banter.

"Hardly."

"I don't mean to intrude," Lestrade cut in. "But have you decided to help us or not?" Sherlock spun to look at Lestrade, a wolfish grin spreading on his features. His dark cobalt eyes gleamed, sending a shiver down John's spine.

"Show me."

The game was afoot.

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**Follow and review your thoughts! Do you think I should continue with this story? This is my first time writing a Sherlock fan fiction, so feedback would be much appreciated! **


	2. Chapter 2

John Hamish Watson was extremely annoyed.

Would no one explain what was going on? Lestrade was walking several meters ahead, his head held high as he found himself in his element. One look at the rugged man could tell you he was in charge of the situation from the way he held himself. Christ, he even looked the part of the leader, what with his hawkish eyes and solid jaw.

Tailing Lestrade eagerly was Sherlock, his eyes already tearing apart the tranquil morning at the zoo into cold bare facts. John, for his part, was trying to keep his temper in check. All he had to go on was the zoo's plastic sign pointing in the direction they were heading. John peered at the sign eagerly.

The Snake House.

Not very helpful, but at least John could stop fantasizing the brutal gruesomeness of say, a lion's attack. Still, this did not sate John's curiosity.

"Is anyone going to-" John started, and then abruptly stopped when he noticed that Sherlock had frozen in the middle of the path. John hesitated only briefly before cautiously walking up to the young man's side. Sherlock's eyes were trained on a cage to their right. Inside was a small metal gymnasium and half a dozen chimpanzees. Sherlock's eyes were questioning, as though he was trying, but failing, to deduce something. John could practically see the question marks floating next to his head. Sherlock could sweep into a crime scene and identify a murderer in a heartbeat, but something about this cage seem to honestly puzzle the detective.

"Sherlock?" John asked gently. He regretted it immediately as Sherlock's concentration broke at the sound of John's voice. Sherlock inhaled sharply and flinched.

_Flinched?_

The young detective had actually had a physical reaction to John's sudden words, his eyebrows furrowing suddenly as though in pain. John immediately put his hand on his strange friend's arm comfortingly, confused by the sudden turn of events. John was used to Sherlock's odd behaviors and mood swings, but this felt different.

If asked, John wouldn't be able to say _what _exactly was different. Sherlock would slip in and out of his mind palace at the oddest and most inconvenient times. He was prone to strange or even absurd fixations of the simplest of things, whether it was the flight of a bird through the London smog or the softness of one of John's jumpers. John could easily brush aside this instance as Sherlock simply being Sherlock.

And yet, something held John back. He craned his neck and looked up at friend's eyes. The kaleidoscope of dark blues shone briefly with startling clarity.

His cobalt eyes held the look of a lost child. He looked almost... scared.

John's mind was sent reeling, and John reflexively tightened his grip on his friend. Something was horribly wrong. Something John hadn't seen-

John could feel Sherlock's arm tense as he snapped out of his revere. Glancing down at John before his eyes flickered away uneasily, Sherlock abruptly started walking, taking long strides in order to catch up with Lestrade. John stood still for a moment, shocked, before whirling around and running after Sherlock.

"Wha- what is it?" John asked, watching as Sherlock tightened his coat around himself despite the warming temperature. Sherlock ignored him, his shoulders hunched in a way John knew said to stay away. John ignored Sherlock's body language and grabbed his shoulder before the pair reached Lestrade.

"Bloody hell, Sherlock!" John hissed, making his friend face him. Sherlock looked down at John reproachfully. John held himself like a soldier, his grip firm and his back straight. "What happened back there?" John asked, his voice giving no room for argument.

"Nothing." Sherlock sniffed stubbornly.

"We both know that isn't true." John said sternly, his bright eyes penetrating. Sherlock squirmed uneasily under his gaze.

"You'll laugh." Sherlock said wryly, a shrewd smile gracing his lips that didn't quite reach his humorless eyes.

"You didn't laugh when you found out my limp was psychosomatic." John answered honestly. It had left a deep impression on John when Sherlock hadn't judged him for his limp. John would never forget his friend's acceptance, nor would he underestimate the power of a faithful friend. Something was bothering Sherlock, and John would be damned if he let his friend hide it from him. "I won't laugh."

Sherlock searched John's strong face. The army doctor's amount of loyalty never ceased to astound him. Sherlock slowly let out the breath, controlled and even.

"I-" Sherlock started, looking ahead anxiously at the obvious Detective Inspector. Sherlock lowered his voice, his eyes never leaving John's. "I- I don't like zoos." Sherlock said tightly.

John blinked.

This man, who constantly experimented on corpses, examined gruesome crime scenes, and made a point to catch nuclear bombers before teatime was uncomfortable at a _zoo_? Busloads of schoolchildren came through every day. Just meters away was a brightly-coloured booth selling cheap merchandise, complete with t-shirts and plastic safari hats.

The great Sherlock Holmes was actually intimidated by a zoo.

Why?

But true to his word, John didn't laugh. Instead he nodded and gave Sherlock's shoulder a reassuring squeeze.

"Right." John said. "Well, don't worry. We'll be out of here as soon as we examine the crime scene, all right?"

"I'm not _worried_." Sherlock said defensively.

"I know." John replied simply. Whatever was bothering Sherlock wasn't worrying him... if John had to guess, it was haunting him.

John understood that feeling all too well.

"Come on." John said awkwardly, one hand slipping into his pocket and the other one traveling to Sherlock's back. "Let's hurry so we can leave- I haven't had my morning cuppa yet."

Sherlock's mouth twitched upward in a small smile as he looked down at John. Though Sherlock wasn't the sentimental type, John could see the unspoken thanks in his eyes and accepted it unquestioningly.

John didn't understand what had made Sherlock seem so… lost. Something about his expression earlier had been deeply sad. John didn't understand what had caused it, but he was determined for it never to hurt his friend again.

Together they walked along in companionable silence, Sherlock's long strides shortening as to stay by John's side.

John's arm was still against Sherlock's back comfortingly, though they both chose to ignore it.

At least, they both pretended to.

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**Suggestions are accepted and treasured- I have an idea of how I want the story to go, but there are still bits (mainly the _middle_) of the story that can be changeable.**


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